Replace read-then-subtract pattern in collectAndReport with atomic
swap-to-zero to eliminate race where AddTraffic increments counters
between snapshot and clearReportedTraffic, causing residual traffic
to accumulate indefinitely and inflate user flow counters.
Also add defensive check in processFlowItem to skip AddFlow when
forward no longer exists, and send DeleteService to clean up orphaned
agent services.
- Add NodeMetric/TunnelMetric/ServiceMonitor models and repository methods
- Implement metrics ingestion service with per-minute bucket aggregation
- Add health checker for node connectivity monitoring
- Wire node metrics from WebSocket SystemInfo messages
- Add tunnel metrics ingestion from flow upload endpoint
- Create monitoring REST API endpoints for nodes, tunnels, services
- Implement service monitor CRUD and execution (TCP/ICMP checks)
- Add MonitorPermission for non-admin access control
- Create frontend monitor page with node/tunnel/service views
- Add tunnel metrics ingestion from agent flow reports
- Include schema migration for tunnel_metric unique index
- Fix tunnel entry port conflict validation to use transaction
Entire-Checkpoint: 030821a7c8e3
sagitchu